upsert.py

import sqlite3

UPDATE_SQL = '''
UPDATE phonebook
SET phone = ?
WHERE name = ?
'''

INSERT_SQL = '''
INSERT INTO phonebook
VALUES (?, ?)
'''

def upsert(cursor, name, phone):
    '''Update or insert phone for name'''
    cursor.execute(UPDATE_SQL, (phone, name))
    if cursor.rowcount > 0:
        return
    cursor.execute(INSERT_SQL, (name, phone))

def main():
    schema = '''
    CREATE TABLE phonebook (
      name TEXT PRIMARY KEY,
      phone TEXT
    );
    '''

    db = sqlite3.connect(":memory:")
    cur = db.cursor()
    cur.executescript(schema)

    upsert(cur, "daffy", "555-555-5555")
    upsert(cur, "daffy", "555-555-5556")

    cur.execute("SELECT phone FROM phonebook WHERE name=?", ("daffy",))
    print(cur.fetchone()[0])

if __name__ == "__main__":
    main()